Circulating pump sealing system



April 29, 1947. ||.l GARTMANN 2,419,681

CIRCULATFNG PUMP SEALING SYSTEM Filed Jan. 8, -1944 2 sheets-sheet 2 NSs Patented Apr. 29, 1947 star T OFFICE CIRCULATNG P SEG SYSTEMApplication January 3, 1944, Seriali No. 51.7,@@55

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This invention relates to a sealing system for a pump and. inparticular, to a system for sealing against boiler pressure a pump usedfor eiecting forced circulation through a boiler. l

The packing oi a centrifugal pump used for circulating purposes ineonnection'with a forcedcirculation boiler presents very substantialdifficulties in view of the fact that the suctionl of the pump issubjected to the high boiler pressure, and corresponding hightemperature, and conventional packing will not withstand such pressuresand temperatures. It is the broad object of the pres` ent invention toprovide a system in which effective packing against high boilerpressures may be secured. Specifically, this is accomplished by the useoi' a combined labyrinth and carbon seal with control of pressures toinsure that th'ere is applied to the carbon seal no more pressure thanthis seal is capable of withstanding, the sealing member being steam.Since steam has a much larger specific volume than water at the sametemperature, the use of steam, as lcompared with that of water, in theconventional breakdown seal, results in decreased weight flow throughthe labyrinth seal.

The foregoing broad object of the invention and more specific objectsrelating particularly to details of construction andoperation willbecome apparent from the following description read in conjunction withthe accompanying drawings, in which:

Figure l is a diagrammatic illustration of a boiler circulating pump andauxiliary devices involved in a system constituting a preferred em.-bodiment of the invention;

Figure 2 is a vertical section through a circu lating pump provided inaccordance with the invention; and

Figure 3 is a similar View of a somewhat dierent type of pump in whichthe packing is effected in a diiferent fashion.

Referring first to Figures 1 and 2, therev is indicated at 2 the drumofa boiler with which a circulating pump 6 is associated, this pumpbeing arranged to receive water from the boiler through the connection 4and to discharge the water through twin outlets 8 and I0 communicating,respectively, with tube systems I2 and I4 of the boiler which areconnected at I6 and I8, respectively,"with the boiler drum. The boileritself forms `no part of the present invention, and it maybe of any ofthe usual types involving forced circulation.

Feed water for Athe boiler enters at 20 a boiler feed pump 22 ofcentrifugal multistage type which may be turbine driven, utilizing steamfrom the boiler. It will be assumed, for purposes of description, thatthis feedpump is of a six-stage type inasmuch as in the presentinstance, a connection is made to an intermediate stage establishing adesired pressure conditoin. The feed water from the pump 22 passesthrough a check valve 2611i the line 2S to an economizer 28, whence itenters the boiler drum at 3B.

Steam from the boiler drum 2 is provided through the line 32 connectedto a superheater 34 from which the steam passes through the line 38 tothe point o use. For purposes of discussion, some figures for a typicalinstallation vmay be cited. The boiler, for example, may be designed tovdeliver steam at 975 lbs. per square inch and a temperature of 543 F.Under these conditions, the boiler feed pump may deliver water at 1150ibs. per square inch at a temperature of 232 F., receiving the feedwater, for example, at 50 lbs. per square inch at about the sametemperature. Under these same conditions, the circulating pump mayprovide a pressure increase of 35 lbs. per square inch so as tointroduce the circulating water to the boiler tube systems at 1010 lbs.per square inch and 543 F.

A carbon, or other seal of conventional type may be provided towithstand pressures of th'e order of 300 lbs. per square inch, and thepresent invention is designed to secure a pressure on such seal limitedto that amount.

, Referring, particularly, to Figure 2 showing the circulating pump 6 indetail, this pump comprises an inlet passage 38 to which the line 4connects, the inlet passage serving to provide flow of water to theinlet eye 4u of the impeller 42 which discharges into the chamber 44communicating withI the twin discharge passages 46. The impeller may belocated, for example, about 8 ft. below the level of water in the boilerdrum so that the suction pressure involves a static head of about 8 ft.in addition to the boiler drum pressure. If, as illustrated, the pumpimpeller is of the singlesuction over-hung type with the water flowingdownwardly therein, there is provided a. selfventing arrangement similarto that common at .the present time for low submergence condensatepumps. Under such conditions, the pump will operate without noise orcavitation. The impeller is mounted on a Vertical shaft 48 driventhrough reduction gearing 50, 52 from a turbine (not shown). In order tobalance some of the upward thrust caused by the action of the boiler.pressure on the area of the shaft at the packing. the lower wearingring assembly 54 is made 3 of greater diameter than the upper wearingring assembly 56.

Connections 56 and 60 to the steam line 32 provide steam saturated atboiler pressure to the chamber 62 through which passes the shaft 48.

` From this chamber 62, flow of steam takes place both upwardly anddownwardly. In flowing downwardly, it passes through the labyrinthinepacking 63 to the chamber 64 which is connected through the passage B6to the chamber 68 of a regulating valve involving a valve member 10Aadapted to permit the bleeding of steam from the chamber 68 into thechamber 12 which is connected through the line 14 to the fourth stage ofthe six-stage boiler, feed pump as indicated at 16.-

In such fourth stage, for example, the pressure is about 785 lbs. persquare inch. The connection to such an intermediate pressure pointpermits the pressure drop between the chambers 68 and 12.

from the chamber 62 to the region 64, there is` insurance against thepossibility that any water from the pump will pass upwardly through thepacking 18 into the chamber 80, so that the steam passing into the line82 can contain only the small amount of moisture which may result fromthe expansion through the labyrinthine packing 18. By reason of thesubmergence of the impeller, the pressure at the suction is greater thanthe steam pressure bythe amount of submergence which, for example, mayamount to about 21/2 lbs. per square inch. Since the pressure inconnection 66 is maintained by the regulating valve below the pressureat the impeller eye, lwater will flow upwardly through the labyrinthinepacking 65 into the chamber 64 to pass with the steam through theregulating valve.

The carbon packing indicated at 84 can withstand the pressure in thechamber 80. A connection 86 leads ofi the leakage of steam to a sump.

Cooling water for the lower bearing may be provided from the boiler feedpump through the connection 88'.

To insure the proper pressure in the line 66 at, for example, 965 lbs.per square inch, the regulating valve 10 is controlled by connection toa diaphragm 92 in a housing 94. The lower side of the diaphragm isexposed through the line 90 to steam which is at boiler pressure. Theupper side of the` diaphragm is subjected to the pressure vin thechamber 68. A spring 95, adjustable through the medium of a screw 98,exerts the proper differential pressure on the diaphragm 92 so that inthe example given, the pressure in 68 is always 10 lbs. per square inchless than the boiler pressure. A In this fashion, the pressure in thechamber 64 is maintained to insure a proper slow rate of flow bothdownwardly from the chamber -62 and upwardly from 4. wise being used ina system such as that shown in Figure 1. In this case, the pump |00comprises the impeller |02 receivingwater at boiler pressure through thepassage |04 and discharging it into the chamber |06 connected throughone or more passages |01 to the tube systems of the boiler. Above theimpeller is the chamber I|0 which is maintainedat a. pressure slightlylbelow the suction pressure by the provision of an auxiliary impeller|08 at the back of the regular pump impeller but slightly larger indiameter. Since this auxiliary impeller is of larger diameter anddischarges into the same 'chamber |06 as' the impeller |02, it willbeevident that this dif-- ference in pressure is secured. A connection||2 -chamber I I6 downwardly through the packing ||8 to meet `thecooling water in ||0, whereby it is condensed so that the impeller |08will handle water only to insure that it maintains the differential inpressure which is required.

Steam from the chamber I |6 may flow upwardly through the labyrinthinepacking |20 to the chamber |22 where, as in the preceding modification,the pressure may be about 300 lbs. per square inch, capable of beingwithstood by the carbon packing |26 and of supplying auxiliaries throughthe connection |24. The steam drain outlet |28 may lead to a sump.

It will be clear from the above that loss of water at the hightemperature and pressure of the boiler is either completely prevented orminimized to a negligible degree by the arrangements in accordance withthe invention, this being effected by the use of a relatively smallamount of steam usable for the driving of auxiliaries, while thepressure on carbon or similar packing is maintained within a limit whichit is capable of withstanding. `It will be obvious that various changesin thel details of the invention may be made without departing from itsscope as defined in the following claims.

What I claim and desire to protect by Letters Patent is:

1. In a forced-circulation boiler system, a'boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forced,circulation of liquid through the boiler, a shaft mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage at'boiler pressure, means providing a chamber about the shaft,means yconnecting said chamber to the vapor space oi' said boiler, meansrestricting iiow along the shaft between said-chamber and said packingthereby to reduce the pressure of vapor reaching the packing to a safevalue substantially below that in said chamber, a second chamber aboutthe shaft on the side of the first chamber opposite said packing, meansfor maintaining in the second chamber a pressure below both the pressurein the first chamber and the suction pressure of the impeller, and meansfor restricting ow along the shaft from the rst chamber to the secondchamber, said arrangement preventing passage of liquid from the impellerto the first chamber.

2. In a forced-circulation boiler system, a

amasar boiler, a centrifugal impeller, means connecting said impeller tothe boiler for forced circulation of liquid through the boiler, a shaftmounting said impeller, packing for the shaft, said packing being of atype liable to damage at boiler pressure, means providing a chamberabout the shaft, means connecting said chamber to the vapor space ofsaid boiler, means restricting flow along the shaft between said chamberand said packing thereby to reduce the pressure of vapor reaching thepacking to a safe value substantially below that in said chamber, asecond chamber about the shaft on the side of the iirst chamber oppositesaid packing, means for maintaining in the second chamber a pressurebelow both the' pressure in the first chamber and .the suction pressureof the impeller, said last mentioned means comprising a device formaintaining in the second chamber a pressure at a predetermineddifferential -below the boiler pressure, and means for restricting iiowalong the shaft from the iirst chamber to the second chamber, saidarrangement preventing passage of liquid from the impeller to the firstchamber.

3. In a forced-circulation boiler system, a boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forcedcirculation of liquid through the boiler, a shaft mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage at boiler pressure,

means providing a chamber about the shaft,

means connecting said chamber to thev vapor space of said boiler, meansrestricting flow along the shaft between said chamber and said packingthereby to reduce the pressure o f vapor reaching the packing to a safeValue substantially be` low that in said chamber, a second chamber aboutthe shaft on the side oi the firstv chamber oppo, site said packing,means for maintaining in the second chamber a pressure below both thepressure in the first chamber and the suction pressure of the impeller,a multiple stage boiler feed pump, said last mentioned means comprisingmeans controlling connections between the second chamber and anintermediate stage of the feed pump to control flow of fluid between thesecond chamber and the feed pump to maintain said required pressure, andmeans for restricting ow along the shaft from the first chamber to thesecond chamber, said arrangement preventing passage of liquid from theimpeller to the first chamber.

4. In a forced-circulation boiler system, a boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forcedcirculation of liquid through the boiler, a shaft mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage at boiler pressure, means providing a chamber about the shaft,means connecting said chamber to the vapor space of said boiler, meansrestricting flow along the shaft between said chamber and said packingthereby to reduce the pressure of vapor reaching the packing to a safevalue substantially below that in said chamber, a second chamber aboutthe shaft on the sideof the rst chamber opposite said packing, means formaintaining in the second chamber a pressure below both the pressure inthe first chamber and the suction pressure of the impeller, a multiplestage boiler feed pump, said last mentioned means comprising meanscontrolling connections between the secmined dierential below boiler'pressure, and means for restricting fiow along the shaft from the firstchamber to the second chamber, said arrangement preventing passage ofliquid from the impeller to the first chamber. V

5. In a forced-circulation boiler system, a boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forcedcirculation of liquid through the boiler, a shaft'mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage kat boiler pressure, means providing a chamber about the shaft,means connecting said chamber to the vapor space of said boiler, meansrestricting flow along the shaft between said chamber and said packingthereby to reduce the pressure of vapor reaching' the packing to a safevalue substantially below that in said chamber, a second chamber aboutthe shaft on the side of the rst chamber opposite said packing, meansfor maintaining in the second chamber a. pressure below both thepressure in the rst chamber and the suction pressure of the impeller,said last mentioned means comprising an auxiliary impeller, and meansfor restricting flow along the shaft from the rst chamber to the secondchamber, said arrangement preventing passage of liquid from the impellerto the first chamber.

6. In a forced-circulation boiler system, a boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forcedcirculation of liquid through the boiler, a shaft mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage at boiler pressure, means providing a chamber about the shaft,means connecting said chamber to the vapor space of said bollen, meansrestricting ow along the shaft between said chamber and said packingthereby to reduce the pressure of vapor reaching the packing to a safeValue substantially below that in said chamber, a second chamber aboutthe shaft on the side of the rst chamber-opposite said packing, meansfor maintaining in the second chamber a pressure below both the pressurein the rst chamber and the suction pressure of the impeller, said lastmentioned means comprising an auxiliary impeller receiving iiuid fromthe second chamber and discharging into the same region as vthe mainimpeller, and means for restricting flow along the shaft from the iirstchamber to the second chamber, said arrangey ment preventing passage ofliquid from the imond chamber and an intermediate stage of the peller tothe rst chamber.

7. In `a forced-circulation boiler system, a boiler, a centrifugalimpeller, means connecting said impeller to the boiler for forcedcirculation of liquid through the boiler, a shaft mounting saidimpeller, packing for the shaft, said packing being of a type liable todamage' at'boiler pressure, means providing a chamber about the' shaft,means connecting said chamber to the vapor space of said boiler, meansrestricting flow along the shaft between said chamber and said packingthereby to reduce the pressure of Vapor reaching the packing to a safevalue substantially below that in said chamber, a second chamber aboutthe shaft on the side of the first chamber opposite said packing, meansfor maintaining in the second chamber a pressure below both the pressurein the rst chamber and the suction pressure of the impeller, said lastmentioned means comprising an auxiliary impeller receiving fluid fromthe second chamber and discharging into the same region as the mainimpeller, means for directing relatively cool feed water lventingpassage of liquid from the impeller to the first chamber.

, HANS GARTMANN.

REFERENCES The following references are of record in the lo le of thispatent:

Number UNITED STATES PATENTS Name Date Spilimann e- Jan. 27, 1942Vorkauf Aug, 15, 1939 Verkauf Aug, 15, 1939 Zwilling Aug. 22, 1939 BeyerJan. 1, 1935 Karassik Jan. 29, 1946

